Utilization of cellular, and other radio, communication systems has achieved wide popularity in recent years. Communications between a mobile terminal and a network station can be effectuated without a wireline connection. Communications can therefore be effectuated when the use of a wireline connection would be inconvenient or impractical.
Cellular networks, for instance, have been installed to encompass many geographic areas. When a mobile terminal operable to communicate by way of such a cellular network is within range of the network, wireless communication by way of the network can be effectuated.
To ensure that apparatus manufactured by different manufacturers are operable in a selected cellular system, standards have been promulgated which define operational parameters of selected ones of such systems. Constructing apparatus which is operable pursuant to the promulgated, operational parameters ensures that such apparatus shall be operable in the selected system.
AMPS (Advanced Mobile Phone Service), TACS (Total Access Communication System), DAMPS (Digital Advanced Mobile Phone Service), GSM (General System for Mobile communications) and PDC (Pacific Digital Cellular) cellular communications systems are all exemplary of cellular communication systems for which standards have been promulgated. In each of such standards, standardized protocols are set forth. Such protocols define communication procedures which permit communications with a mobile terminal operable in the respective communication systems.
For instance, such standards define procedures to be carried out when a call is to be terminated at a mobile terminal. Typically, when a call is to be terminated at a mobile terminal, the mobile terminal is first paged on a paging channel. The page, typically including the mobile station identity (MSI), provides an indication to the mobile terminal that the call is to be terminated at the mobile terminal.
Once a mobile terminal responds to a page, control information is provided to the mobile terminal. For example, control information is provided to the mobile terminal to instruct the mobile terminal to tune to a particular traffic channel, thereby to permit the mobile terminal to receive the call transmitted upon the traffic channel to the mobile terminal.
Because the mobile terminal is, at least potentially, inherently mobile, the precise position in which the mobile terminal is located is not necessarily known. That is to say, there is a certain level of uncertainty regarding the precise position at which a mobile terminal is located.
Periodic, or other, registration procedures are typically carried out when the mobile terminal is in an idle mode of operation. The purpose, in part, of a registration is to provide the network with an indication of the position at which the mobile terminal is located. In a registration procedure, a mobile terminal reports its whereabouts by accessing a network station at regular intervals, e.g., every fifteen minutes. The network station which receives the registration report is indicative of the position in which the mobile terminal is located. By such registration, the mobile terminal also indicates to the network station that the mobile terminal is in an on-state and ready to receive a terminating call if placed thereto. Conversely, in the absence of a registration for a longer time than the periodic registration interval, the network of the communication system is able to determine that the mobile terminal has been turned-off or has moved beyond the coverage area of the communication system.
In at least several of the above-noted communication systems, location areas are defined. Location areas are defined to be groups of cells. Each base station of the cellular network infrastructure defines, typically, a small number of, e.g., three cells. The term "base station" is used in a generic sense herein. It should be understood that a base station refers generally to a cell site formed of one or more transceivers with similar properties and the term cell refers to a geographical area encompassed by the cell site.
In an AMPS or TACS communication system, a location area is a fixed area. In a PDC system, the location area is centered about a cell whereat the mobile terminal is registered. And, in a communication system defined in EIA/TIA Standard Document IS-136, a location area is defined for a particular mobile terminal by providing the mobile terminal with a list of cells which together define the location area. When a mobile terminal travels out of one location area and into another location area, the mobile terminal also transmits a registration report to the network. The location area is usually determinative in such systems of the paging area throughout which a page is transmitted when a mobile terminal is paged.
When the mobile terminal is to be paged, a page is broadcast upon a paging channel to the mobile terminal. The page is repeated one or more times in the event that the mobile terminal does not acknowledge reception of a page broadcast thereto. If the mobile terminal is located beyond the range of the communication system or is turned-off (i.e., in an inactive state), the mobile terminal does not detect the page and does not acknowledge detection thereof. But, additionally, if the mobile terminal is temporarily not tuned to the paging channel upon which the page is broadcast, the mobile terminal also is unable to detect the page. And the page might be transmitted upon a channel which exhibits excessive levels of interference or fading, preventing reception of the page at the mobile terminal. Therefore, broadcast of a page must often have to be repeated. Because, however, the paging channel is of limited capacity, the number of pages broadcast to a mobile terminal should be minimized. The need repeatedly to page a mobile terminal throughout a large area, i.e., a large number of cells, is contrary to the goal of minimizing usage of the paging channel.
To maximize the number of pages which can be broadcast to the mobile terminal without exceeding a paging channel capacity requires that the size of the paging area be minimized. However, reduction in the size of the paging area should not be accompanied by a corresponding increase in mobile terminal registration reports. Such an increase would increase the registration load imposed upon the communication system. Each additional registration report would increase the load imposed upon the network.
There is a need to balance the competing requirements of minimizing the paging load imposed upon the communication system and minimizing the registration load imposed upon the communication system.
AMPS and TACS cellular communication systems are typically constructed in manners to optimize paging response time. Paging load has, historically, not been a significant concern. That is to say, in such systems paging is performed simultaneously throughout a paging area formed of an entire location area, typically formed of between thirty and one hundred-fifty cells. If the page is required to be rebroadcast, the paging area is increased, to be formed of, e.g., three to five location areas.
The need to broadcast a page throughout a paging area formed of several location areas sometimes occurs as a result of "across the border" registration of a mobile terminal. Such a registration occurs when a mobile terminal located in one location area registers with a base station associated with another location area. Broadcasting a page throughout a number of location areas requires the utilization of significant paging resources.
Knowledge of the particular cell in which the mobile terminal had most-recently registered has been superfluous as at least an entire location area is paged. Therefore, even though the identity of the cell in which the mobile terminal was located when the mobile terminal last accessed the communication network is known, such information has not previously been used or otherwise stored to be utilized to page a mobile terminal. Only the identity of the location area in which the mobile terminal is located has been utilized to page the mobile terminal.
With increased usage of such communication systems, the signaling capacity of the communication system is, sometimes, exceeded.
A manner by which to utilize the identity of the cell last accessed by a mobile terminal to make more efficient the paging procedures by which to page a mobile terminal would be advantageous.
Utilization of such information would not significantly increase registration reports as such information is already inherently provided to the network. But advantageous utilization of such information would permit more efficient paging procedures to be utilized to page a mobile terminal.
It is in light of this background information related to paging procedures in a radio communication system to page a mobile terminal that the significant improvements of the present invention have evolved.